2020 Monkeymatic Mixcube

[xtian]

Boy-o-boy you're on to something now - mic it up with a large-diaphragm condenser that's as big as the speaker cab. Then use the same speaker to assess your mono mixdown. Diabolical!

Tease. No, but really, I am enjoying this little box as a guitar speaker. I ordered some tiny Class D amp boards. 8-24vDC input, up to 60w output into 2 ohms. I'm curious to see how much power I can get with 9vDC and 8ohms. I just need a couple of watts of clean power, really.

[Leo_Gnardo]

Boy-o-boy you're on to something now - mic it up with a large-diaphragm condenser that's as big as the speaker cab. Then use the same speaker to assess your mono mixdown. Diabolical!

Tease. No, but really, I am enjoying this little box as a guitar speaker. I ordered some tiny Class D amp boards. 8-24vDC input, up to 60w output into 2 ohms. I'm curious to see how much power I can get with 9vDC and 8ohms. I just need a couple of watts of clean power, really.

No tease intended - there's an advantage to small, light speaker cones for guitar recording. Think of all the tracks that were recorded with a Champ. And I've done sessions where the setup I mentioned was used - U87's parked in front of a pair of little Roland mini stereo cubes - the sound was terrific. Also live shows where Crate's version of a Champ was mic'd up with an Audio-Technica large diaphragm mic, model 4033 if I remember right. Yes, it looked silly but can't fault the sound quality. And nobody was hassling the guitarist for playing too loud.

[xtian]

I received my TPA3118 amp module today, and set about testing its output power. I knew the 60 watt rating (with 24vDC and 2 ohm load) was marketing BS, but still...the most I could coax was 20 watts into 2 ohm resistive load. I didn't let it run long, though, as the temp was rushing past 200°F and I didn't want to melt the rubber eraser I was using to hold the thermo probe on the chip.

At 9vDC and 460mA, I get one watt clean output into 8 ohms. That's fine, exactly what I was hoping, and the temp hovers around 100–120°F. That will be enough power for this little speaker, and no heat sink required.

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[xtian]

I wired the input with a 1/8" (3/5mm) stereo jack, mixed down to mono using this circuit:



This makes the amp howl, with nothing plugged into the jack. If I do a simple mono input, no howl. Anyone can think why?

[EDIT: I simply removed the 20K resistor, and all is good.]

[xtian]

Finally wrapped this up, having received a 4PDT switch to allow passive/active switch (input and output grounds are not shared, so DPDT would not do the job).

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